Two-wire controlling and monitoring system for irrigation of localized areas of soil

ABSTRACT

A two-wire controlling and monitoring system for irrigation of localized areas of soil includes a water pipeline, a plurality of controllable irrigation valves, a plurality of field sensors measuring specific irrigation parameters, and a plurality of localized irrigation control units. Each irrigation control unit has a sensor decoder connected to a specific field sensor and/or a line decoder connected to a specific controllable irrigation valve. The system further includes a controller and power supply unit that applies a first alternating DC voltage signal to a two-wire cable interconnecting the controller and power supply unit and the irrigation control units. The two-wire cable provides power from the controller and power supply unit to each of the irrigation control units, it transmits schedules of instructions to the irrigation control units through the two-wire cable, and it receives the irrigation parameters from the irrigation control units through the two-wire cable.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a Continuation of co-pending U.S. application Ser.No. 10/886,395, filed Jul. 7, 2004, which is a Continuation of U.S.application Ser. No. 09/721,462, filed Nov. 22, 2000, now U.S. Pat. No.6,766,221, which is a Continuation of International Application No.PCT/DK00/00635, filed Nov. 15, 2000. The disclosures of these priorapplications are incorporated herein by reference.

BACKGROUND OF THE INVENTION

This particular invention relates generally a two-wire controlling andmonitoring system particularly for irrigation of localized areas ofsoil.

The most commonly known two-wire irrigation control systems, such ascontrol systems disclosed in US patents U.S. Pat. No. 4,007,458 and U.S.Pat. No. 4,176,395 hereby incorporated by reference, provide control ofa number of remotely located irrigation or sprinkler valves from acentral location by means of control signals encoded on to a single pairof power transmission lines linking a central encoder and a number ofremote decoders.

The two-wire irrigation control system according to U.S. Pat. No.4,007,458 encodes and transmits an address of a specific remotelylocated irrigation valve and on/off signals onto an alternating currentsignal (AC) by clipping half portions of the signal to represent zerovalues.

Similarly the two-wire interactive irrigation control system accordingto U.S. Pat. No. 4,176,395 transmits data by selectively clipping theoriginal power frequency signal during eight consecutive cycles,suppressing the power frequency signal during the following full cycle,during which time a feedback signal may be transmitted from sensorslocated at specific areas, then transmitting eight undistorted powerfrequency cycles, and suppressing the power frequency signal for onefollowing cycle, during which time a feedback signal relating to aportable operator may be transmitted.

Both two-wire irrigation control systems according to U.S. Pat. No.4,007,458 and U.S. Pat. No. 4,176,395 communicate to remotely locatedirrigation valves or decoders by clipping of the power signalsconsequently while performing a transmission on the power line power tothe remotely located irrigation valves or decoders is significantlyreduced.

Furthermore the two-wire irrigation control systems according to U.S.Pat. No. 4,007,458 and U.S. Pat. No. 4,176,395 utilizes sinusoidalsignals for transmitting power to remotely located irrigation valves ordecoders. Sinusoidal signals being AC signals generally need to beconverted into DC in order to drive microprocessor electronic circuitryadding total costs of the two-wire irrigation systems for theelectronics incorporated in the remotely located irrigation valves ordecoders.

SUMMARY OF THE INVENTION

An object of the present invention is to provide a two-wire controllingand monitoring system for in particular controlling a plurality ofcontrollable irrigation or sprinkler valves placed at specific localizedareas, monitoring specific irrigation parameters at the specificlocalized areas and communicating through a two-wire cable with line andsensor decoders located at the specific localized areas while limitingabove described power loss due to signaling on the two-wire cable.

A particular advantage of the present invention is utilization of apower supply signal for the operation of the controllable irrigationvalves hence performing an improved power transmission within generalsafety specifications.

A particular feature of the present invention is an improved corrosionresistance.

The above object, the above advantage and the above feature togetherwith numerous other objects, advantages and features which will beevident from the below detailed description of a preferred embodiment ofthe present invention is according to a first aspect of the presentinvention obtained by a two-wire controlling and monitoring system forin particular irrigation of localized areas of soil and comprising:

a water pipeline providing water to said localized areas of soil,

a first plurality of controllable irrigation valves each positioned at aspecific area of said localized areas of soil, communicating with saidwater pipeline, providing watering or non-watering of said specific areaof said localized areas of soil and having a pair of valve controlinputs,

a second plurality of field sensors positioned at specific areas of saidlocalized areas of soil, providing specific irrigation parameters andhaving a pair of sensor outputs,

a third plurality of localized irrigation control units each comprisinga sensor decoder having a pair of sensor inputs connected to said pairof sensor outputs of a specific field sensor of said second plurality offield sensors for providing power to said second plurality of fieldsensors and recording said specific irrigation parameters from saidsecond plurality of field sensors and/or a line decoder having a pair ofvalve control outputs connected to said pair of valve control inputs ofa specific controllable irrigation valve of said first plurality ofcontrollable irrigation valves for providing valve control signals tosaid first plurality of controllable irrigation valves, said sensordecoder and said line decoder further each having a pair of control andpower supply inputs,

a controller and power supply unit having a set of schedules ofinstructions and having a pair of control and power outputs supplyingpower by applying a first alternating DC voltage signal defining avoltage maximum having a first pulse width and defining a voltageminimum having a second pulse width to one of said pair of control andpower outputs, simultaneously applying a second alternating DC voltagesignal similarly shaped but of inverted polarity as compared to saidfirst alternating DC voltage signal to another of said pair of controland power outputs and applying an alternating DC current defining acurrent maximum having a third pulse width and defining a currentminimum having a fourth pulse width to said pair of control and poweroutputs,

a two-wire cable interconnecting said controller and power supply unitand said third plurality of localized irrigation control units andconnecting said pair of control and power outputs of said controller andpower supply unit to said control and power inputs of said thirdplurality of localized irrigation control units and providing said powerfrom said controller and power supply unit to each of said thirdplurality of localized irrigation control units, and

said controller and power supply unit transmitting said schedules ofinstructions to said third plurality of localized irrigation controlunits through said two-wire cable and receiving said specific irrigationparameters from said third plurality of localized irrigation controlunits through said two-wire cable. According to the basic realization ofthe first aspect of the present invention the application of twoalternating DC voltage signals having respectively inverted polarity onto the two-wire cable provides an improved power transmission withrespect to prior art's application of sinusoidal voltage signals. Theimprovement is approximately by a factor of 2. Sinusoidal voltagesignals although ideal for some purposes impose a restriction on maximumattainable power transmission during a time frame caused by the inherentshape of the voltage signal squared as compared to a square wave voltagesignal squared. Furthermore, by relying on slow alternating DC voltagesignals for powering of the decoders instead of relying on sinusoidalvoltage signals having standard 50 Hz or 60 Hz network frequencies aless noise sensitive and subsequently cheaper circuit may beimplemented, since relatively little attention should be given to noiseconsiderations. Additionally, the square wave structure of thealternating DC voltage signal provides an ideal platform for carryingbinary information, which will be further described below.

The water pipeline characteristic of the two-wire irrigation controllingand monitoring system according to the first aspect of the presentinvention is wholly or partly buried under ground, or the water pipelineis placed on the ground. Parts of the pipelines being above ground levelprovide movable sections that may easily be moved into positionsaccording to the conditions of the local areas. Furthermore the waterpipeline is constructed from plastic materials or metal materials suchas iron steel, copper, silver, gold or any alloys thereof in anycombinations thereof. Generally plastic tubes are favorable since theprice is low with respect to metal material pipes and since plastictubes are more flexible rendering it possible to rearrange the layout ofthe pipes without causing severe expenses. The first plurality ofcontrollable irrigation valves according to the first aspect of thepresent invention are magnetically, electrically, hydraulically orpneumatically operated or combinations thereof. The first plurality ofcontrollable irrigation valves according to the first aspect of thepresent invention is preferably electrically operated and opened byapplying an inrush voltage or current signal followed by a hold voltageor current signal to the pair of valve control inputs and closed byapplying no voltage or current signal to the pair of valve controlinputs. Further according to the first aspect of the present inventionthe line decoders provide the inrush voltage, the hold voltage and thezero voltage to the first plurality of controllable irrigation valves bysupplying from the pair of valve control outputs a pulsed alternating DCcontrol signal to the pair of valve control inputs in accordance withthe transmitted schedules of instructions. The pulsed alternating DCvoltage signal defines a maximum differential voltage in the range of25V to 45V such as ranges 27V to 43V or 30V to 40V or preferably themaximum differential voltage is 35V, defines a minimum differentialvoltage in the range of 0V to 5V such as ranges 0V to 3V or 0V to 1V orpreferably the minimum differential voltage is 0V and defines a linedecoder output pulse width in the range of 10 μs to 0.1 s such as ranges200 μs to 2 ms or 800 μs to 1.25 ms or preferably the line decode outputpulse width is 1 ms. The line decoder output pulse width defines a firstpart having the maximum differential voltage and a second part havingthe minimum differential voltage. The pulsed alternating DC voltagesignal constitutes the inrush voltage by having the first part longerthan or equal to the second part during a period in the range 10 ms tois such as 30 ms to 100 ms and constitutes the hold voltage by havingthe first part shorter than the second part during a period determinedin accordance with the schedule of instructions transmitted to the linedecoders by the controller and power supply unit. The parts may have anyparticular lengths to provide for any composition of signals generatinga wide variety of average voltages, however the composition describedabove is optimal for driving an electrically driven irrigation valvewith respect to power consumption of the line decoder.

The first pulse width of the first and second alternating DC voltagesignals according to the first aspect of the present invention is equalto the second pulse width, is smaller than the second pulse width or isgreater than the second pulse width. Preferably the first pulse width issubstantially equal to the second pulse width thereby constituting asquare wave voltage signal.

The first alternating DC voltage signal and the second alternating DCvoltage signal according to the first aspect of the present inventionalternate with a frequency less than AC frequency of power networks suchas 50 Hz or 60 Hz. The first pulse width of the first alternating DCvoltage signal and the second alternating DC voltage signal is in therange 100 ms to 10 s such as ranges 200 ms to 2 s, 300 ms to 1 s, 400 msto 800 ms, 450 ms to 550 ms, 475 ms to 525 ms or 490 ms to 510 ms, orpreferably the first pulse width is 500 ms and the second pulse width ofthe first alternating DC voltage signal and the second alternating DCvoltage signal is in the range 100 ms to 10 s such as ranges 200 ms to 2s, 300 ms to 1 s, 400 ms to 800 ms, 450 ms to 550 ms, 475 ms to 525 msor 490 ms to 510 ms, or preferably the second pulse width is 500 ms. Byreducing frequency of alternation, toggling or inversion of the firstand the second alternating DC voltage signals the noise sensitivity ofthe circuitry is reduced and furthermore the tolerances as to acceptableaccuracy of pulse widths is shifted from μs range to ms range.

The first alternating DC voltage signal and the second alternating DCvoltage signal according to the first aspect of the present inventionduring the first pulse width and the second pulse width averagesvoltages greater than or equal to zero voltage. Alternatively, the firstalternating DC voltage signal and the second alternating DC voltagesignal during the first pulse width and the second pulse width averagesvoltages less than or equal to zero voltage. In particular the firstalternating voltage signal and the second alternating voltage signalduring the first pulse width and the second pulse width averages anaverage voltage in the range −5V to −0.5V such as ranges −4V to −1V or−2.5V to −1.5V, or preferably the average voltage is −2V. The voltagemaximum of the first and second alternating DC voltage signals accordingto the first aspect of the present invention is in a range from +10V to+20V, such as ranges +13V to +19V or +14V to +17V, or preferable thevoltage maximum is +15V and the voltage minimum in a range from −15V to−25V, such as ranges −17V to −23V and −19V to −21V, or preferable thevoltage minimum is −20V. By applying a numerically larger minimumvoltage compared to maximum voltage off setting the average voltagebelow ground voltage the risk for deterioration of the two-wire cablecaused by corrosion is significantly reduced since the deterioration ofthe two-wire cable at locations where the presence of an insulatinglayer around the two-wire cable has been damaged will be based on analkaline process. The alkaline process donates electrons to the groundlevel due to the voltage difference and accepts a layer of ionssubstituting the missing electrons and thus the layer of ion creates asaturation layer at the exposed part of the two-wire cable reducingfurther corrosion of the two-wire.

The maximum current according to the first aspect of the presentinvention is in the range of 0.5 A to 2 A such as 0.75 A to 1.5 A ande.g. preferably the maximum current is 1.1 A, and the minimum current isin the range 20 mA to 150 mA such as ranges 30 mA to 100 mA or 35 mA to85 mA, or preferably the minimum current is 40 mA. Additionally, thethird pulse width defining a part of the alternating DC current signalis greater than the fourth pulse width, and the fourth pulse widthdefining another part of the alternating DC current signal is in therange 0.1 ms to 10 ms such as range 0.5 ms to 7 ms or preferably thefourth pulse width is shorter than 5 ms. The alternating DC currentsignal provides low current sequences during which communication may beperformed from irrigation control units placed at specific locations tothe controller and power supply unit.

Communication from the controller and power supply unit to theirrigation control units placed at specific locations may consist ofschedules of instructions according to the first aspect of the presentinvention. The schedules of instructions are transmitted onto thetwo-wire system by re-scaling the first pulse width or the second pulsewidth of the first and second alternating DC voltage signals to a fifthpulse width in the range 10 ms to 49 ms such as ranges 15 ms to 35 ms or17 ms to 25 ms, or preferably the fifth pulse width is 20 ms indicatinga binary “1”, or by re-scaling the first pulse width or the second pulsewidth of the first and second alternating DC voltage signals to a sixthpulse width in the range 0.5 ms to 9 ms such as ranges 1 ms to 8 ms or 2ms to 5 ms, or preferably the sixth pulse width is 5 ms indicatingbinary “0”. By modulating pulse width of the first and secondalternating DC voltage signals instead of clipping of portions of thevoltage signals significantly improves power transmission from thecontroller and power supply unit to the irrigation control units whileproviding ingenious means for communication.

The transmitted schedules of instructions according to the first aspectof the present invention comprise a type declaration determiningadditional content of a transmission from the controller and powersupply unit to the third plurality of localized irrigation controlunits. The additional content such as an address of a specificdesignated localized irrigation control unit of the third plurality oflocalized irrigation control units, data disclosing informationregarding actions to be taken by the specific designated localizedirrigation control unit of the third plurality of localized irrigationcontrol units and/or a first check and a second check ensuring a safereception of the transmission is terminated by stop signal having aseventh pulse width. The seventh pulse width is in the range 50 ms to 70ms such as 55 ms to 65 ms, or preferably the seventh pulse width is 60ms. The content of transmissions may have numerous purposes and achievenumerous tasks and provide means for performing a wide variety oftransmissions comprising a plurality of information types.

The above described type declaration comprising 4 bits provides 16optional operations such as Arbitration, Data, Control (On/Off),Broadcast, Test and Pole leaving room for still 10 possible operationswhich according to today's needs is sufficient. However an increase ofthe transmission size of the type declaration to 8, 16 or 32 bits willeven further expand the possible variety of operations.

The address of the specific designated localized irrigation control unitof the third plurality of localized irrigation control units comprisesan address transmission size in the range 0 to 128 bits such as ranges 0to 64 bits or 0 to 32, or the address transmission size is preferably 16bits. The address transmission size determines the maximum number ofpossible communicative or addressable irrigation control units connectedto the controller and power supply. Therefore, if additional irrigationcontrol units are needed for either operation of sensors or control ofirrigation valves the address transmission size may be extendedaccordingly. The data disclosing information regarding actions to betaken by the specific designated localized irrigation control unit ofthe third plurality of localized irrigation control units comprises adata transmission size in the range of 0 to 64 KBYTE. The data containedin a transmission may include information regarding timing of openingand closing of the controllable irrigation valves, however the data mayinclude a wide variety of information.

The first check and the second check ensuring a safe reception of thetransmission comprise a check transmission size in the range 0 to 128bits such as ranges 0 to 64 bits or 0 to 32 bits or preferably the checktransmission size is 4 bits for each of the first and second check. Thefirst and second check provides means for checking if transmittedinformation has been properly received.

The controller and power supply unit according to the first aspect ofthe present invention comprises a microprocessor, a storage unit forstoring the schedules of instructions, an output section for providingpower to the two-wire cable and transmitting the schedules ofinstruction on the two-wire cable, and an input section for monitoringvoltage of the two-wire cable. An interrupt window is initiatedfollowing a DC alternation of the first alternating DC voltage signaland the second alternating DC voltage signal and a power supply period.The power supply period is in the range 250 ms to 550 ms such as ranges300 ms to 500 ms or 350 ms to 450 ms, or preferably the power supplytime period is 400 ms and the interrupt window is in the range of 0 msto 20 ms or preferably the interrupting window is shorter than 5 ms. Themicroprocessor controls the output section to apply the minimum currentto the two-wire cable during an interrupt window. The interrupt windowallows the sensor decoders or line decoders to perform an interruptduring which the decoders may communicate information to the controllerand power supply unit.

Each of the sensor decoders and/or line decoders comprises a shortcircuiting circuit providing an interrupt signal during the interruptwindow to the controller and power supply unit by unidirectional shortcircuiting the pair of control and power supply inputs hence reducingdifferential voltage of the two-wire cable and no interrupt signal byopen circuiting the pair of control and power supply inputs. Theinterrupt signal is constituted by a voltage drop of the differentialvoltage of the two-wire cable in the range 5V to 35V such as range 15Vto 30V, or preferably the voltage drop is 25V thus the differentialvoltage is 10V. Hence the voltage of the two-wire cable during theinterrupt signals is negative relative to ground voltage e.g. −10V andtherefore the alkaline process described earlier is maintained duringinterrupt signals. The microprocessor records the interrupt signal fromat least one sensor decoder and/or line decoder of the third pluralityof localized irrigation control units through the input sectionmonitoring voltage of the two-wire cable and subsequently operates theoutput section to perform a DC alternation of the first alternating DCvoltage signal and the second alternating DC voltage signal and operatesthe output section to terminate the interrupt window and apply themaximum current to the two-wire cable. Additionally, the microprocessorfollowing a recording of the interrupt signal from at least oneinterrupting sensor decoder and/or line decoder of the third pluralityof localized irrigation control units performs a DC alternation of thefirst alternating DC voltage signal and the second alternating DCvoltage signal and transmits the type declaration Arbitration followedby a series of binary “1”s including an answer window for the at leastone interrupting sensor decoder and/or line decoder of the thirdplurality of localized irrigation control units to answer as describedbelow to the binary “1”. The answer window is initiated following a DCalternation of the first alternating DC voltage signal and the secondalternating DC voltage signal and a pause period, the pause period is inthe range 2 ms to 10 ms such as ranges 3 ms to 8 ms or 4 ms to 6 ms, orpreferably the pause period is 5 ms. The answer window is in the rangeof 0 ms to 20 ms or preferably the answer window is shorter than 2.5 ms.The series of binary “1”s constitute an opportunity for the interruptingdecoder to answer yes or no during an answer window in accordance withthe interrupting decoder's address. By selecting a series of binary “1”sfor obtaining the address from the interrupting decoder the shortestArbitration transmission is achieved since in case of severalinterrupting decoders the decoder with the lowest address will beaddressed first and decoders with higher addresses will be addressedsubsequently at next possible interrupt.

As in the case of the interrupt signal the short circuiting circuitprovides an answer signal during the answer window to the controller andpower supply unit by unidirectional short circuiting the pair of controland power supply inputs hence reducing differential voltage of thetwo-wire cable and no answer signal by open circuiting the pair ofcontrol and power supply inputs. The answer signal is constituted by avoltage drop of the differential voltage on the two-wire cable in therange 5V to 35V such as range 15V to 30V, or preferably the voltage dropis 25V or the differential voltage is 10V. Hence the voltage of thetwo-wire cable during the answer signals is negative relative to groundvoltage e.g. −10V and therefore the alkaline process described above ismaintained during the answer window. The microprocessor interprets theanswer signal as an indication of a binary “0” and no answer signal as abinary “1”.

The microprocessor according to the first aspect of the presentinvention further controls the output section to supply the minimumcurrent to the two-wire cable during the answer window, so as to avoidunnecessary power loss caused by answering decoders transmission ofbinary “0”s. As soon as the answer from the answering decoder isdetected by the controller and power supply unit the controller andpower supply unit applies the maximum current to the two-wire cable.Hence the power loss is significantly reduced as compared to techniquesin state of the art control irrigation systems.

The second plurality of field sensors according to the first aspect ofthe present invention comprises a selection of temperature sensors,humidity sensors, pressure sensors, magnetic field sensors, mechanicalmovement sensors, mechanical strain sensors, flow sensors, fertilizersensors or any combination thereof. The objective of these sensors is toprovide specific parameters giving a complete picture of the conditionsof the specific localized areas and may further be implemented in a widevariety of ways in order to obtain specific requested informationregarding the conditions of the ground. A further objective of thesesensors is to provide irrigation parameters giving a complete picture ofthe working conditions, functionality and operation of the controllableirrigation valves.

The controller and power supply unit according to the first aspect ofthe present invention during a declared type of transmission ofschedules of instructions requests the specific irrigation parametersfrom an addressed sensor decoder of the third plurality of localizedirrigation control units and subsequently the controller and powersupply unit transmits a series of binary “1” including the answer windowfor the addressed decoder to answer to the binary “1”. Themicroprocessor records the answer signal from at least one sensordecoder of the third plurality of localized irrigation control unitsthrough the input section monitoring the voltage of the two-wire cableand operates the output section to perform a DC alternation of the firstalternating DC voltage signal and the second alternating DC voltagesignal and subsequently operates the output section to terminate theanswer window and apply the maximum current to the two-wire cable. Theterm DC alternation is to be conceived as a generic term for toggle,inversion or switching between the maximum and minimum voltages of thefirst and second alternating DC voltage signal. By implementing thecommunication from the irrigation control units as described above aseries of advantages are achieved. The two-wire irrigation controllingand monitoring system consumes little power during normal operation andduring transmission of information between the controller and powersupply unit and the irrigation control units. By accomplishing thetransmission of information using a pulse width defining a binary “1”and a pulse width defining a binary “0” the two-wire irrigationcontrolling and monitoring system provides an undisturbed powertransmission at the same time as exchange of information.

The above objects, the above advantages and the above features togetherwith numerous other objects, advantages and features which will beevident from the below detailed description of a preferred embodiment ofthe present invention is according to a second aspect of the presentinvention obtained by a method for controlling and monitoring inparticular irrigation of localized areas of soil and comprising thefollowing steps of:

providing water to said localized areas of soil through a waterpipeline,

controlling discharge or supply of water from said water pipeline,providing watering or non-watering of a specific area of said localizedareas of soil through a first plurality of controllable irrigationvalves each positioned at said specific area of said localized areas ofsoil and said first plurality of controllable irrigation valves having apair of valve control inputs,

measuring specific irrigation parameters through a second plurality offield sensors positioned at said specific areas of said localized areasof soil and said second plurality of field sensors having a pair ofsensor outputs,

transmitting control signals to said first plurality of controllableirrigation valves and said second plurality of field sensors though athird plurality of localized irrigation control units comprising asensor decoder and a line decoder, providing valve control signals tosaid first plurality of controllable irrigation valves and/or recordingsaid specific irrigation parameters from said second plurality of fieldsensors, each of said third plurality of localized irrigation controlunits having a pair of valve control outputs connected to the pair ofvalve control inputs of a specific controllable irrigation valve of saidfirst plurality of controllable irrigation valves and/or a pair ofsensor inputs connected to said pair of sensor outputs of a specificfield sensor of the second plurality of field sensors and having a pairof control and power supply inputs,

providing a set of schedules of instructions by means of a controllerand power supply unit having a pair of control and power outputssupplying power by applying a first alternating DC voltage signaldefining a voltage maximum having a first pulse width and defining avoltage minimum having a second pulse width to one of the pair ofcontrol and power outputs, simultaneously applying a second alternatingDC voltage signal similarly shaped but of inverted polarity as comparedto said first alternating DC voltage signal to another of said pair ofcontrol and power outputs and applying an alternating DC currentdefining a current maximum having a third pulse width and defining acurrent minimum having a fourth pulse width to said pair of control andpower outputs,

providing a two-wire cable, interconnecting said controller and powersupply unit and said third plurality of localized irrigation controlunits through a two-wire cable connecting said pair of control and poweroutputs of said controller and power supply unit to said control andpower inputs of said third plurality of localized irrigation controlunits and providing said power from said control and power unit to eachof said third plurality of localized irrigation control units, and

transmitting said schedules of instructions from said controller andpower supply unit to said third plurality of localized irrigationcontrol units through said two-wire cable and receiving said specificirrigation parameters from said third plurality of localized irrigationcontrol units through said two-wire cable.

The method according to the second aspect of the present inventiondescribes operation of a two-wire controlling and monitoring systemwhich includes any of the above discussed features and provides a methodfor achieving significant reductions in power consumption relative totoday's state of the art.

The above objects, the above advantages and the above features togetherwith numerous other objects, advantages and features which will beevident from the below detailed description of a preferred embodiment ofthe present invention is according to a third aspect of the presentinvention obtained by a localized irrigation control unit for a two-wirecontrolling and monitoring system including a controller and powersupply unit and for in particular irrigation of localized areas of soiland said localized irrigation control unit comprising:

a field sensor decoder for receiving input signals from a field sensor,converting said input signals to a binary number and transmitting saidbinary number to said controller and power supply unit, and

a line decoder for receiving instructions from said controller and powersupply unit or a mark sender unit, converting said instructions to acontrol signal and providing said control signal to a controllableirrigation valve.

The localized irrigation control unit according to the third aspect ofthe present invention provides means for irrigating of the localizedareas, means for measuring of specific irrigation parameters describingthe conditions of the localized areas, means for communicating with themark sender unit and means performing communication with the controllerand power supply unit. The localized irrigation control unit circuitrymay be implemented for carrying out communication on a two-wireconducting cable, but may however be implemented for carrying outcommunication on optic cables or be implement for carrying outcommunication through radio transmitted signals. The input signalscomprising analogue voltage signals, analogue current signals, digitalpulse count signals, digital pulse width modulation signals or digitalpulse frequency modulation signals or any combinations thereof. The marksender provides the possibility for manually controlling the operationof the controllable irrigation valves irrespective of the schedules ofinstructions transmitted by the controller and power supply unit. Themark sender ensures that an operator may initiate irrigation atlocalized areas by transmitting control signals to the controllableirrigation valve from the mobile mark sender.

The sensor decoder included in the localized irrigation control unitaccording the third aspect of the present invention comprises a fieldsensor power supply and field sensor signal amplifier having a pair ofsensor inputs connected to a pair of sensor outputs of a specific fieldsensor, a control and power supply input section having pair of controland power supply inputs connected to a two-wire cable interconnectingthe sensor decoder and the controller and power supply unit, a shortcircuiting circuit having switching means connected between the pair ofcontrol and power supply inputs, and a first microprocessor unitinterconnecting the field sensor power supply and field sensor signalamplifier and the short circuiting circuit.

The line decoder included in the localized irrigation control unitaccording the third aspect of the present invention comprises a controland power supply input section having a pair of control and power supplyinputs connected to the two-wire cable interconnecting the line decoderand the controller and power supply unit, a valve control power outputstage having at least one pair of valve control outputs connected to apair of valve control inputs of a specific controllable irrigation valveand a second microprocessor unit interconnecting the control and powersupply input section and the valve control output.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a schematic overview of the two-wire controlling andmonitoring system according to the preferred embodiment of the presentinvention.

FIG. 2 shows in perspective a localized irrigation control unitaccording to the preferred embodiment of the present invention andinterconnecting a two-wire cable and a controllable irrigation valve incommunication with a water pipeline, and the localized irrigationcontrol unit further being connected to a field sensor.

FIG. 3 shows alternating DC voltage signals versus time provided from acontroller and power supply unit on the two-wire cable to at least oneof the localized irrigation control units.

FIG. 4 shows alternating DC current signal versus time applied by thecontroller and power supply unit on to the two-wire cable and receivedby at least one of the localized irrigation control units.

FIG. 5 shows a control voltage signal versus time provided by a linedecoder in one of the localized irrigation control units to one of thecontrollable irrigation valves.

FIG. 6 shows a transmission of schedules of instructions provided by thecontroller and power supply unit to the localized irrigation controlunits.

FIG. 7 shows an example of the contents of a transmission from thecontroller and power supply unit to the localized irrigation controlunits.

FIG. 8 shows a alternating DC voltage line signal transmitted on oneconductor of the two-wire cable and corresponding alternating DC currentsignal between conductors of the two-wire cable.

FIG. 9 shows a differential voltage signal between conductors of thetwo-wire cable and the corresponding two alternating DC voltage linesignals.

FIG. 10 shows a transmission of a type declaration followed by asequence of binary “1”s including an answer window.

FIG. 11 shows a circuit diagram of the presently preferred embodiment ofa sensor decoder.

FIG. 12 shows a circuit diagram of the presently preferred embodiment ofa line decoder having one valve control output.

FIG. 13 shows a circuit diagram of the presently preferred embodiment ofa line decoder having at least one valve control output.

FIGS. 14 a and 14 b show a circuit diagram of a microprocessor andstorage section included in a controller and power supply unit accordingto a preferred embodiment of the present invention.

FIGS. 15 a and 15 b show a circuit diagram of a power output stageincluded in a controller and power supply unit according to a preferredembodiment of the present invention.

FIGS. 16 a and 16 b show a circuit diagram of a mark sender according toa preferred embodiment of the present invention.

DETAILED DESCRIPTION OF THE PRESENT INVENTION

The two-wire controlling and monitoring system designated by numeral 10in its entirety and shown in FIG. 1, provides irrigation of localizedareas e.g. a golf course having certain areas needing a particularamount of irrigation and others a smaller amount of irrigation, parkshaving tree sections, lawns or flower beds all needing particularamounts of irrigation, greenhouse production lines having a series ofproduction steps for plants, flowers or vegetables all needing aparticular amount of irrigation or farming fields having a variety ofproduce needing a variety of amounts of irrigation.

The two-wire controlling and monitoring system 10 has an inletconnection 12 supplying water from a general household water pumpstation or a water tank to a pump 14. The pump 14 is mechanically,pneumatically, hydraulically, electrically or magnetically driven ordriven by combinations thereof and provides a water pressure on a waterpipeline 16 enabling the water pipeline 16 to supply water to aplurality of localized irrigation control units 18 positioned at aseries of localized areas of soil 20.

The water pipeline 16 may be constructed from metal pipes produced inmaterials such as iron, steel, copper, aluminum, silver, gold or anyalloys thereof and/or plastic pipes produced in materials such as PVC,PP or PE or any combinations thereof.

The localized irrigation control units 18 are positioned at the seriesof localized areas of soil 20 and provide irrigation to specific areasof each of the localized areas of soil 20 through a plurality of localpipelines 22 possibly mounted with sprinkling gadgets 24. The localizedirrigation control units 18 utilizes connections 40 and the pump 14utilizes connections 26 to communicate through a two-wire cable 28interconnecting a controller and power supply unit 30 with the pluralityof localized irrigation control units 18 and the pump 14. The controllerand power supply unit 30 transmits power and schedules of instructionsto the plurality of localized irrigation control units 18.

The controller and power supply unit 30 comprises a keyboard 32 for auser to communicate schedules of instructions i.e. controlling timing ofirrigation and position of irrigation to be stored and executed by acomputer 34. The controller and power supply unit 30 further comprises amonitor 36 for displaying the operation of the two-wire controlling andmonitoring system 10 and a printer 38 for printing out information fromthe computer 34. The computer 34 may include a an internal or externalmodem through which remotely monitoring and controlling of the computer34 is achieved and thereby remotely monitoring and controlling of thecontroller and power supply unit 30. The computer 34 may further haveaccess to internet facilities which similarly provides the possibilityfor remotely monitoring and controlling of the computer 34 and therebythe controller and power supply unit 30. Additionally, a series ofcomputers for example operating irrigation monitoring and controllingsystems like the computer 34 may be monitored and controlled from acentral unit located at any position world-wide hooked up to theinternet or connecting to the series of computers through use of modems.

The localized irrigation control units 18 are situated in a housing orcabinet 46, shown in FIG. 2, made of a wear resistant material such asmetals like aluminum or steel or plastics like PVC, PP or PE. Thehousing 46 protects the localized irrigation control units 18 from anyhostile environment the housing is positioned in.

Each of the localized irrigation control units 18, as shown in FIG. 2,may comprise a controllable irrigation valve 42 controlling release ofwater from the water pipeline 16 and a line decoder 44 transmitting thenecessary schedules of instructions to the controllable irrigation valve42.

The controllable irrigation valve 42 may be magnetically, electrically,hydraulically or pneumatically operated or combinations thereof,however, according to the presently preferred embodiment of theinvention the controllable irrigation valve 42 is electrically operatedthrough connectors placed in a connector box 48 in the housing 46. Theconnector box 48 comprises a solenoid, which controls the valve in anopen or closed position. Variations of current applied to the solenoidcause the induction of magnetic fields, which subsequently activate thevalve.

The line decoder 44 receives transmissions of schedules of instructionsfrom the controller and power supply unit 30 through the two-wire cable28. A pair of control and power inputs 40 connects the line decoder 44to the two-wire cable 28. A pair of valve control outputs 50 connectsthe connector box 48 to the line decoder 44. The line decoder 44 appliescontrol signals 100 to the connector box 48 through the pair of valvecontrol outputs 50, which control signals 100, described in furtherdetail below with reference to FIG. 5, are further communicated by theconnector box 48 to the controllable irrigation valve 42. Alternativelythe line decoder 44 may receive start instructions through radiotransmissions produced by a mobile handhold mark sender providing theopportunity to initiate irrigation at specific localized areasregardless of schedules of instructions. This enables manual control ofthe controllable irrigation valves 42.

The localized irrigation control unit 18 further comprises a sensordecoder 52, as shown in FIG. 2, recording a specific irrigationparameter from a field sensor 54 through a pair of sensor outputs 56 andproviding a conversion of the specific irrigation parameter measured bythe field sensor 54 to a binary number and additionally performing atransmission of the binary number to the controller and power supplyunit 30. The sensor decoder 52 is connected to the two-wire cable 28through a pair of control and power inputs 58. The specific irrigationparameters may be soil or air temperature, soil or air humidity, waterpressure in the water pipeline 16, water flow in the water pipeline 16or water flow through one of the controllable irrigation valves 42.Furthermore the specific irrigation parameters may be mechanicalmovement, mechanical strain or magnetic fields which may be utilized forthe determination of the functionality or operation of the controllableirrigation valves 42.

The line decoder 44 and the sensor decoder 52 receive power through thetwo-wire cable 28 from the controller and power supply unit 30. FIG. 3shows voltage versus time curves of a first alternating DC voltagesignal, designated by LA, and a second alternating DC voltage signal,designated by LB, simultaneously provided by the controller and powersupply unit 30 to the two-wire cable 28 for powering of the line decoder44 and the sensor decoder 52.

The first alternating DC voltage signal LA has a positive pulse with apulse width 64 in the range 450 ms to 550 ms and a negative pulse with apulse width 66 in the range 450 ms to 550 ms. In the presently preferredembodiment of the invention the pulse width 64 is substantially equal to500 ms, and the pulse width 64 and the pulse width 66 are substantiallyequal.

The first alternating DC voltage signal LA has a maximum voltage 146 inthe range of +10V to +20V and has a minimum voltage 148 in the range of−15V to −25V. In the presently preferred embodiment of the invention themaximum voltage 146 is +15V and the minimum voltage 148 is equal to−20V.

The first alternating DC voltage signal LA is symmetrical about a line142 indicating a negative off set voltage of the first alternating DCvoltage signal LA, in the presently preferred embodiment of theinvention the off set voltage is approximately −2V.

The second alternating DC voltage signal LB is inverted in comparisonwith the first alternating DC voltage signal LA and has a negative pulsewith a pulse width 68 in the range 450 ms to 550 ms and a positive pulsewith a pulse width 70 in the range 450 ms to 550 ms. In the presentlypreferred embodiment of the present invention the pulse width 68 issubstantially equal to 500 ms and the pulse width 64, the pulse width66, the pulse width 68 and the pulse width 70 are substantially equal.

The term inverted in this context means a phase shift between the firstalternating DC voltage signal LA and the second alternating DC voltagesignal LB of approximately 180°.

The second alternating DC voltage signal LB has a maximum voltage 60 inthe range of +10V to +20V and has a minimum voltage 62 in the range of−15V to −25V. In the presently preferred embodiment of the invention themaximum voltage 60 is equal to the maximum voltage 146 of the firstalternating DC voltage signal LA, and the minimum voltage 62 is equal tothe minimum voltage 148 of the first alternating DC voltage signal LA.

The second alternating DC voltage signal LB is symmetrical about a line144, which line 144 indicates a negative off set voltage of the secondalternating DC voltage signal LB. In the presently preferred embodimentof the invention the off set voltage of the second alternating DCvoltage signal is approximately equal to the off set voltage of thefirst alternating DC voltage signal.

By off setting the first and the second alternating DC voltage signalsLA, LB with a negative voltage relative to ground 140 a substantiallyslower corrosion of the two-wire cable 28 is achieved. In case ofnegative off set, the current will run from the ground level 140 tocopper material of the two-wire cable 28 resulting in an alkalineprocess, which is less hazardous to the copper material than an electronacceptor donating process relative to ground level 140, achieved in caseof positive off set forcing the current to run from the copper materialto the ground level 140.

FIG. 4 shows a current versus time curve of an alternating DC currentsignal 80 provided by the controller and power supply unit 30 betweenthe wires of the two-wire cable 28. The alternating DC current signal 80has a maximum current 78 in the range of 0.5 A to 2 A, and has a minimumcurrent 76 in the range of 20 mA to 150 mA. In the presently preferredembodiment of the invention the maximum current 78 is 1.1 A and theminimum current 76 is 40 mA.

The alternating DC current signal 80 furthermore has a pulse width 72defining the period of minimum current 76 of the alternating DC currentsignal 80, which pulse width 72 is in the range 0.1 ms to 10 ms, and hasa pulse width 74 defining the period of maximum current 78 of thealternating DC current signal 80. In the presently preferred embodimentof the invention the pulse width 72 is shorter than 5 ms and the pulsewidth 74 is lesser than 500 ms. The length of the pulse width 74 isdepending on which operation is performed by the controller and powersupply unit 30. In case of an Arbitration or data transferringtransmission consisting of a series of binary “1”s then the pulse width74 is shorter than 20 ms. During normal operation the pulse width 74however, is shorter than 500 ms.

FIG. 5 shows a voltage versus time curve of the control signal 100provided by the line decoder 44 to the controllable irrigation valve 42.The control signal 100 consists of an inrush signal 102 and a holdsignal 104. The inrush signal 102 provides a maximum voltage 82 foroperating the controllable irrigation valve 42 in an open positionenabling water to flow from the water pipeline 16 to the local pipeline22 positioned in the localized areas 20. The inrush signal 102 defines apulse width 88 in the range 10 ms to is in the presently preferredembodiment of the invention the pulse width 88 is in the range 30 ms to100 ms. When the controllable irrigation valve 42 is completely opened,the line decoder 44 changes the control signal 100 from the inrushsignal 102 to the hold signal 104. The hold signal 104 has a reducedmaximum voltage 84. The line decoder 44 continues to transmit the holdsignal 104 as long as dictated by the schedules of instructions. As soonas the control signal is turned off providing ground voltage 86 to thecontrollable irrigation valve 42, the controllable irrigation valve 42closes and thereby disables the flow of water from the water pipeline 16to the local pipeline 22.

In order to reduce power consumption of the controllable irrigationvalves 42 the control signal 100 in the presently preferred embodimentof the invention is construed from a series of square wave pulses 114constituting an pulsed inrush signal 110 and constituting a pulsed holdsignal 112. The square wave pulse 114 defines a voltage maximum 92having a pulse width 94 and defines a voltage minimum 90 having a pulsewidth 96 in the pulsed inrush signal 110 and defines the voltage maximum92 having a pulse width 99 and defines the voltage minimum 90 having apulse width 98 in the pulsed hold signal 112. According to a firstembodiment of the present invention the pulse width 94 and the pulsewidth 96 and the pulse width 99 are 1 ms, but may be any value in therange 100 μs to 0.1 s. The pulse width 98 is 10 ms, but may be any valuein the range 6 ms to 30 ms. The average voltage of the pulsed inrushsignal 110 is equal to the maximum voltage 82 of the inrush signal 102and the average voltage of the pulsed hold signal 112 is equal to thereduced maximum voltage 84 of the hold signal 104. According to a secondand presently preferred embodiment of the invention the sum of the pulsewidths 94 and 96 and the sum of the pulse widths 98 and 99 are 1 ms, butmay be any value in the range 100 μs to 0.1 s. During the pulsed inrushsignal 110 the pulse width 94 is substantially larger than the pulsewidth 96 thereby constituting an average voltage of the pulsed inrushsignal 110 equal to the maximum voltage 82 of the inrush signal 102.During the pulsed hold signal 112 the pulse width 98 is substantiallygreater than the pulse width 99, thereby constituting an average voltageof the pulsed hold signal 112 equal to the reduced maximum voltage 84 ofthe hold signal 104.

The maximum voltage 82 of the control signal 100 in the presentlypreferred embodiment of the invention is 35V, but may have any value inthe range 5V to 45V. The minimum voltage 84 of the control signal 100 inthe presently preferred embodiment of the invention is 0V equal toground level 86, but may be in the range 0V to 5V.

The controller and power supply unit 30 transmits schedules ofinstructions simultaneously to transmitting power through the two-wirecable 28 to the line decoder 44. The schedules of instructions aretransmitted to the irrigation control units 18 in a sequential binarypattern 118 construed from alternations or toggling of the firstalternating DC voltage signal LA and the second alternating DC voltagesignal LB. FIG. 6 shows a voltage versus time curve 116 having a normalpattern 126 where the first alternating DC voltage signal LA has thepulse width 64, the maximum voltage 146 and minimum voltage 148 andhaving the binary pattern 118. The sequential binary pattern 118 isprovided by simultaneous alternations of the first alternating DCvoltage signal LA and the second alternating DC voltage signal LB. FIG.6 shows only the first alternating DC voltage signal for simplicity.

The binary pattern 118 defines a binary “1”s by having a pulse width 120in the range 10 ms to 49 ms and defines a binary “0”s by having a pulsewidth 122 in the range 1 ms to 9 ms. In the presently preferredembodiment of the invention the pulse width 120 defining binary “1” is20 ms and the pulse width 122 defining binary “0” is approximately 5 ms.

A transmission of the binary pattern 118 is concluded by a pulse width124 defining a stop signal in the range of 50 ms to 70 ms. In thepresently preferred embodiment of the invention the pulse width 124 is60 ms.

The transmission of schedules of instructions in the form of the binarypattern 118 from the controller and power supply unit 30 to theirrigation control unit 18, is shown as an example in FIG. 7 andaccording to the presently preferred embodiment of the invention thetransmission consists of type declaration 128 defining the type ofoperation needed by the irrigation control unit 18. In the presentlypreferred embodiment of the invention type declarations may be“Arbitration” used for prioritizing functions, “Data” used fortransmitting data to the irrigation control unit 18, “Control” used forswitching line decoders 44 in the irrigation control units 18 on andoff, “Broadcast” used for transmission of data to all irrigation controlunits 18 in the two-wire controlling and monitoring system 10, “Test”used for testing the functionality of one of the irrigation controlunits 18 and “Pole” used for extracting specific irrigation parametersfrom one of the sensor decoders 52 in the irrigation control units 18.

Depending on which type declaration 128 is transmitted, the binarypattern 118 may further consist of an address 130 having a transmissionsize in the range 0 to 128 bits, data 132 having a transmission size inthe range of 0 to 1 Gbits, a first check 134 having a transmission sizein the range of 0 to 128 bits, a second check 136 having a transmissionsize in the range of 0 to 128 bits, and finally the transmission isconcluded by a stop signal 138 defined by the pulse width 124. In thepresently preferred embodiment of the invention, the type declarationconsists of 4 bits, the address 130 consists of 16 bits, the data 132consists of up to 64 KBYTE (1 BYTE equal to 1024 bits), the first check134 consists of 4 bits and the second check 136 consists of 4 bits.

FIG. 8 shows a voltage versus time curve of the first alternating DCvoltage signal LA and simultaneously a curve of current versus time ofthe alternating DC current signal 80. During the positive pulse havingthe pulse width 64 the controller and power supply unit 30 provides aninterrupt window 154 during which the alternating DC current signalapplies the minimum current 76 to the two-wire cable 28 until aninterrupt from the irrigation control units 18 is detected. The pulsewidth 72 of the minimum current 76 part of the alternating DC currentsignal 80 determines the interrupt window's 154 active time period. Inthe presently preferred embodiment of the invention the active timeperiod of the interrupt window is shorter than 5 ms. The precise lengthof the pulse width 72 is determined according to detection by thecontroller and power supply 30 of an interrupt from the irrigationcontrol units 18. As soon as an interrupt is detected during theinterrupt window 154 the DC alternating current signal shifts state andprovides maximum current 78 to the two-wire cable.

The interrupt window 154 follows an alternation 150 of the firstalternating DC voltage signal LA and a power active time period 152. Inthe presently preferred embodiment of the invention the power activetime period 152 is 400 ms.

The sensor decoder 52 comprises a short circuiting circuit forunidirectional short circuiting the pair of control and power inputs 58.The sensor decoder 52 may request an interrupt of the two-wirecontrolling and monitoring irrigation system 10 by unidirectional shortcircuiting the pair of control and power inputs 58 during the interruptwindow 154 and hence provide a voltage drop 158 of a differentialvoltage 156 between the first alternating DC voltage signal LA and thesecond alternating DC voltage signal LB, shown in FIG. 9. FIG. 9 shows avoltage versus time curve of the differential voltage 156 duringtransmission of the request of an interrupt. In the presently preferredembodiment of the invention the maximum voltage of the differentialvoltage 156 is in the range 25V to 45V or preferably 35V and during therequest of an interrupt the differential voltage may drop to a value inthe range 15V to 30V. However, in the presently preferred embodiment ofthe invention the differential voltage may drop to a maximum of 25V orto a voltage of −10V relative to ground voltage.

FIG. 9 furthermore shows voltage versus time curves of the firstalternating DC voltage signal LA and the second alternating DC voltagesignal LB during the request for an interrupt. As FIG. 9 shows, duringthe request of an interrupt performed in the interrupt window 154 thevoltage difference between the first alternating DC voltage signal LAand the second alternating DC voltage signal LB is significantlyreduced, which reduction is detected by the controller and power supplyunit 30. In response to the request of an interrupt the controller andpower supply unit 30 performs an alternation 160 of the firstalternating DC voltage signal LA and the second alternating DC voltagesignal LB and performs a shift in state of the DC alternating currentsignal 80 from minimum current 76 to maximum current 78. Since the shortcircuiting is unidirectional the effect of the short circuit is avoidedfollowing the DC alternation of the first alternating DC voltage signalLA and the second alternating DC voltage signal LB. At the same time theDC alternation indicates to the plurality of irrigation control units 18that the controller and power supply unit 30 has received an interruptfrom one of the plurality of irrigation control units 18 and thereforethe plurality of irrigation control units 18 are prepared for thecontroller and power supply unit's 30 initiation of a transmission 162of the type declaration “Arbitration” on the two-wire cable 28.

FIG. 10 shows a curve of the second alternating DC voltage signal LBtransmitting the transmission 162 comprising a type declaration. If thetype declaration transmitted is “Arbitration” then the controller andpower supply unit 30 continues its transmission by applying a series ofbinary “1”s 168 to the two-wire cable 28 in order to obtain an addressof the interrupting irrigation control unit 18 having the lowestaddress. Each of these binary “1”s includes an answer window 166occurring after a delay 164, during which the minimum current 76 isapplied to the two-wire cable 28. If at least one of the interruptingirrigation control units 18 during the first answer window 166 performsa unidirectional short circuiting of the pair of control and powerinputs 58, then the controller and power supply unit 30 interprets theresulting voltage drop as a binary “0” indicating that the mostsignificant bit of the address of the at least one of the interruptingirrigation control units 18 is “0”. On the other hand if none of theinterrupting irrigation units 18 perform a short circuiting of the pairof control and power inputs 58 during the answer window 166, then thecontroller and power supply unit 30 interprets a binary “1” indicatingthat the most significant bit of the addresses of all of theinterrupting irrigation control units 18 is “1”. Subsequently thecontroller and power supply unit 30 initiates transmission of a secondbinary “1” including a second answer window 166 by performing a newalternation of the first alternating DC voltage signal LA and the secondalternating DC voltage signal LB and applies the maximum current 78 tothe two-wire cable 28. This process is repeated until the controller andpower supply unit 30 has located the interrupting irrigation controlunit 18 having the lowest address. In effect the interrupting irrigationcontrol units 18 answer “yes” or “no” to the transmission of the seriesof binary “1”s 168 in accordance with the interrupting irrigationcontrol units' 18 own address. When the controller and power supply unit30 has identified for example the interrupting sensor decoder 52 bydetecting the sensor decoder's 52 answers in the answer window 166, thenthe controller and power supply unit 30 continues a new transmission ofbinary “1”s including answering windows 166 for the interrupting sensordecoder 52 to transmit data from the sensor decoder 52 to the controllerand power supply unit 30 by answering “yes” or “no”.

Similar communication techniques as described above between thecontroller and power supply unit 30 and the individual irrigationcontrol units 18 is utilized during the controller and power supplyunit's 30 request for data from the irrigation control units 18 andduring any type declaration in which obtaining information from theirrigation control units 18 is required.

Voltage drops outside a designated interrupt window 154 or answer window166 or voltage drops below an acceptable voltage minimum during such awindow (154, 166) may be due to erroneous equipment. Thus voltage dropsfurther may show if the two-wire controlling and monitoring system hasfaulty equipment. Alternatively, the controller and power supply unit 30may establish a separate test window in both high and low pulses of boththe first alternating DC voltage signal LA and the second alternating DCvoltage signal LB. The test window may be initiated following a toggleor alternation of the first and second alternating DC voltage signal LAand LB. According to one embodiment of the present invention the testwindow is initiated 100 ms following a specific pre-selected alternationand has a length of 10 ms. By reducing the alternating DC current signal80 to minimum current 76 during the test window erroneous signaling fromthe irrigation control unit 18 is avoided.

In the presently preferred embodiment of the invention the alternatingDC current signal 80 during the answer window 166 is reduced to theminimum current 76, which minimum current 76 lasts for the pulse width72. The length of the pulse width 72 is determined in accordance withthe earliest response from one of the answering irrigation control units18 and limited to a having a maximum length of 2.5 ms. The answer window166 during a transmission of a series of binary “1”s is initiatedfollowing a non-active time period of approximately 5 ms.

Generally speaking the communication between the controller and powersupply unit 30 and the irrigation control units 18 is implemented byutilizing a unidirectional short circuiting circuit in the irrigationcontrol units 18 for transmitting an interrupt request to the controllerand power supply unit 30 and for transmitting answers to the controllerand power supply unit 30. The reaction of the controller and powersupply unit 30 is immediate alternation and consequently a shorter timehaving minimum current 76 applied to the two-wire cable 28. Even if thereaction of the controller and power supply unit 30 during the processof obtaining information from the irrigation control units 18 during theanswer windows 166 is not restricted in the sense that a binary “0” mustbe 5 ms but rather that a binary “0” is indicated entirely by a shortcircuiting signal from the irrigation control units 18 at any momentwithin the answer window. However, the faster the short circuitingsignal is detected by the controller and power supply unit the betterthe power transfer to the irrigation control units 18 becomes.

The two-wire controlling and monitoring system 10 may be configured in avariety of ways. The presently preferred embodiment of the electronicsof the two-wire controlling and monitoring system 10 is shown in FIGS.11 to 16.

FIG. 11 shows a circuit diagram of the presently preferred embodiment ofthe sensor decoder 52. The circuit diagram shows the short circuitingcircuit 170, a control and power supply input section 186 having pair ofcontrol and power supply inputs designated by Line-A and Line-B, aconstant voltage supply 172, a microprocessor 174 and a field sensorpower supply and field sensor signal amplifier 176.

The short circuiting circuit 170 comprises a differential amplifiermonitoring polarity of the lines Line-A and Line-B and communicationinformation regarding polarity of the lines Line-A and Line-B to themicroprocessor 174. The short circuiting circuit 170 further comprisestwo transistors for unidirectional short circuiting of the lines Line-Aand Line-B. The transistors are controlled by the microprocessor 174 andoperated to open or close during interrupt windows 154 and answeringwindows 166.

The control and power supply input section 186 provides an electricalseparation between the two-wire cable 28 and the sensor decoder 52. Thisis achieved by employing bridge circuitry in combination with areservoir capacitor. During interrupt windows 154 and answering windows166 the current supplied to the two-wire cable 28 is significantlyreduced and therefore in order to keep the sensor decoder functioningduring these short periods the reservoir capacitor supplies the currentneeded for operating the sensor decoder 52.

FIG. 12 shows a circuit diagram of the presently preferred embodiment ofthe line decoder 44 having one valve control output. The circuit diagramshows a control and power supply input section 186 having pair ofcontrol and power supply inputs designated by LA and LB, amicroprocessor 178 and an output power stage 180 for operating thecontrollable irrigation valves 42 to open and closed positions.

FIG. 13 shows a circuit diagram of the presently preferred embodiment ofthe line decoder 44 having at least one valve control output. Thecircuit diagram shows the microprocessor 178 and a plurality 182 of thepower output stage 180 for operating a series of the controllableirrigation valves 42 to open and closed positions.

Similarly to the circuit diagram for the sensor decoder 52 depicted infigure the line decoder 44 shown in FIG. 12 and the line decoder shownin FIG. 13 comprise power supply input sections 186 electricallyseparating the two-wire cable 28 from the internal circuitry of the linedecoders 44 in FIGS. 12 and 13. The power supply input section 186consists of a bridge circuit and a reservoir capacitor.

FIGS. 14 a and 14 b show a circuit diagram of a controller section ofthe presently preferred embodiment of the controller and power supplyunit 30.

FIGS. 15 a and 15 b show a circuit diagram of power supply section ofthe presently preferred embodiment of the controller and power supplyunit 30.

FIGS. 16 a and 16 b show a circuit diagram of a mark sender fortransmitting start information to the controllable irrigation valves 42irrespective of the controller and power supply unit's 30 schedules ofinstructions. The mark sender provides the opportunity for manuallycontrol the controllable irrigation valves 42 to open or close andthereby provide an operator the possibility to manually adjust theirrigation during inspection of for example a golf course.

EXAMPLE

The sensor decoder 52 shown in FIG. 11 and as described above wasimplemented in a prototype version from the following components. FuseP1 230 V Resistors: R1 46R4 R14 39R2 R27 470K R2 46R4 R15 10K R28 470KR3 100K R16 39K R29 56K R4 86K6 R17 39K R30 39K R5 100K R18 10K R31 27K1R6 100K R19 39K R32 39K R7 100K R20 39K R33 56K R8 10K R21 86K6 R34 100KR9 150K R22 4R7 R35 2K49 R10 768K R23 10K R36 825R R11 22K1 R24 10K R372R2 R12 100K R25 10K R38 39K R13 39K R26 10K Capacitors C1 1000μ C6 33pC11 1n C2 10n C7 1n C12 1n C3 100n C8 1n C13 1n C4 10μ C9 100n C5 33pC10 100n Diodes D1 DF04S D6 BYD17D D11 22 V D2 10 V D7 6V8 D12 22 V D3BYD17D D8 LL4148 D13 15 V D4 BYD17D D9 LL4148 D5 BYD17D D10 3V2Transistors Q1 TIP122 Q4 BC856 Q6 MJD6039 Q2 BC856 Q5 BC846 Q7 MJD6039Q3 BC846 Integrated Circuits and Crystal IC1 ST6220 IC3 LM317LM IC5LMC662C IC2 93C05 IC4 LM358N X1 6.144 MHz

The line decoder 44 shown in FIG. 12 and as described above wasimplemented in a prototype version from the following components. FuseP1 200 mA Resistors: R1 470K R6 68K R11 1M R2 100K R7 56K R12 470K R3100K R8 470K R13 1K R4 680K R9 1K R18 1K R5 100K R10 33K R19 3K3Capacitors C1 3n3 C4 10μ C6 1000μ C2 3n3 C5 10μ C7 3n3 C3 3n3 Diodes D1DF04S D3 LL4148 D5 BYD17D D2 BZX84-10V D4 MLL4690 D6 BYD17D TransistorsQ1 BC856B Q3 2SB1214 Q4 2SB1817 Q2 BC856B Integrated Circuits IC1μPD7556 IC2 93C06

The line decoder 44 shown in FIG. 12 and as described above wasimplemented in a prototype version from the following components.Resistors: R1 470K R8 470K R14 3K3 R2 100K R9 1K R15 3K3 R3 100K R10 33KR16 3K3 R4 680K R11 1M R17 3K3 R5 100K R12 68K R18 1K R6 68K R13 1K R193K3 R7 56K Capacitors C1 3n3 C3 2200μ C5 1μ C2 3n3 C4 10μ Diodes D1DF04S D7 BYD17D D13 BYD17D D2 BZX84-10V D8 BYD17D D14 BYD17D D3 LL4148D9 BYD17D D15 BYD17D D4 MLL4690 D10 BYD17D D16 BYD17D D5 BYD17D D11BYD17D D17 BYD17D D6 BYD17D D12 BYD17D Transistors Q1 BC856B Q4 2SB1214Q7 MJD6039 Q2 BC855B Q5 2SB1214 Q8 2SB1214 Q3 2SB1214 Q6 2SB1214 Q92SB1214 Integrated Circuits IC1 μPD7556 IC2 93C06

The microprocessor and storage section shown in FIG. 14 a and 14 b andas described above was implemented in a prototype version from thefollowing components. Resistors: R105 4K7 R14 1M R102 PTC4.3 R104 1K R4680K R101 0R Capacitors and Inductors C101 100μ C108 22n C6 33p C103100n C109 22n C7 33p C104 100n C110 22n L101 10μ C105 100n C111 22n L10210μ C106 100n C112 10μ L103 10μ C107 100n C113 22n Diodes D1 ICTE5 D104BZW06P6V8B D105 BZW06P6V8B Integrated Circuits and Crystal IC101 27256IC108 74HC573 IC4 PC812 IC102 62256 IC110 75175 IC5 PC813 IC103 6264IC111 74HC02 IC6 PC910 IC104 6264 IC112 74HC08 X1 11.0592 IC106 74HC138IC115 4548 IC107 8031 IC116 74HC366

The power output stage shown in FIG. 15 a and 15 b and as describedabove was implemented in a prototype version from the followingcomponents. Resistors: R1 390R R17 487K R34 1K R2 1K R18 10K R35 20K R3Not Used R19 110K R36 1M R4 390R R20 53K6 R37 68R R5 Not Used R21 365KR38 270R R6 100R R22 4R7 R39 47R R7 100R R23 470R R40 100K R8 10K R24470R R51 390K R9 18K R25 27R R52 10K R10 390K R26 27R R53 1K R11A 2R R271K P1 S10K25 R11B 2R R28 47R P2 S10K25 R11C 2R R29 10K P3 S10K25 R11D 2RR30 100K P5 S10K25 R12 1K R31 100K P6 S10K25 R13 1M R32 100K P7 S10K25R15 10K R33 100R R16 14K Capacitors and Inductors C1 Not Used C12 10μC51 100n C2 Not Used C13 10μ C52 1μ C3 Not Used C14 10μ L1 25μ C4 NotUsed C15 22n L2 25μ C5 1n C16 22n RE1 Relay C8 1000μ C20 Not Used C9100μ C21 Not Used C10 100μ C50 100n Diodes D1 BYW98 D6 1N4148 D10 1N4002D2 BYW98 D8 1N4002 D11 1N4002 D4 Z6V8 D9 1N4002 D103 1N4148 D5 Z15V/1WTransistors T1 BC637 T4 BC637 T8 TIP100 T2 BDW74D T5 BDW74D T3 IRFD02 T6IRFE02 Integrated Circuits IC1 LM7812 IC9 4001 IC13 ADC0834 IC2 CA3240AIC10 4053 IC14 44111 IC3 LM340LA IC11 4094 IC15 TCA365A IC7 LM3395 IC124094

The mark sender shown in FIG. 16 a and 16 b and as described above wasimplemented in a prototype version from the following components.Resistors: R1 12R R9 100K R17 10K R2 10K R10 100K R18 56K R3 5K6 R11270K R19 27K R4 22R R12 270K R20 10K R5 2K2 R13 10K R21 1K R6 10K R143K3 R22 100K R7 680R R15 10K R23 10K R8 330R R16 2K2 Capacitors andInductors C1 10μ C6 47n C11 10μ C2 220μ C7 47n C12 100n C3 100n C8 47nC13 220μ C4 220p C9 47n L1 100μ C5 100μ C10 100n Diodes D1 DFO4M D3 10 VD5 3V9 D2 P6KE47A D4 BYW100 D6 1N4148 Transistors T1 IRF9120 T3 IRF110T4 IRF110 T2 BC337 Integrated Circuits and Crystal IC1 80C31 IC5 74HC541IC8 LM324 IC2 26G256 IC6A 74HC95 IC9 7555 IC3 74HC573 IC6B 74HC352 IC10LM317 IC4 X2444 IC7 74HC86 X1 6.144 MHz

1. A two-wire controlling and monitoring system for irrigation oflocalized areas of soil, comprising: a water pipeline providing water tosaid localized areas of soil; a first plurality of controllableirrigation valves, positioned at specific areas of said localized areasof soil, communicating with said water pipeline, providing watering ornon-watering of said specific areas of said localized areas of soil andhaving a pair of valve control inputs; a second plurality of fieldsensors positioned at said specific areas of said localized areas ofsoil, providing specific irrigation parameters and having a pair ofsensor outputs; a third plurality of localized irrigation control unitseach comprising a sensor decoder having a pair of sensor inputsconnected to said pair of sensor outputs of a specific field sensor ofsaid second plurality of field sensors for providing power to saidsecond plurality of field sensors and recording said specific irrigationparameters from said second plurality of field sensors and/or a linedecoder having a pair of valve control outputs connected to said pair ofvalve control inputs of a specific controllable irrigation valve of saidfirst plurality of controllable irrigation valves for providing valvecontrol signals to said first plurality of controllable irrigationvalves, said sensor decoder and said line decoder further each having apair of control and power supply inputs; a controller and power supplyunit having a set of schedules of instructions and having a pair ofcontrol and power supply outputs supplying power by applying a firstalternating DC voltage signal defining a voltage maximum having a firstpulse width and defining a voltage minimum having a second pulse widthto one of said pair of control and power supply outputs, simultaneouslyapplying a second alternating DC voltage signal similarly shaped but ofinverted polarity as compared to said first alternating DC voltagesignal to another of said pair of control and power supply outputs andapplying an alternating DC current defining a current maximum having athird pulse width and defining a current minimum having a fourth pulsewidth to said pair of control and power supply outputs; a two-wire cableinterconnecting said controller and power supply unit and said thirdplurality of localized irrigation control units and connecting said pairof control and power supply outputs of said controller and power supplyunit to said control and power supply inputs of said third plurality oflocalized irrigation control units and providing said power from saidcontroller and power supply unit to each of said third plurality oflocalized irrigation control units; and said controller and power supplyunit transmitting said schedules of instructions to said third pluralityof localized irrigation control units through said two-wire cable andreceiving said specific irrigation parameters from said third pluralityof localized irrigation control units through said two-wire cable. 2.The two-wire irrigation controlling and monitoring system according toclaim 1, wherein said water pipeline is in contact with the ground, andwherein said water pipeline is constructed from a material selected fromthe group consisting of plastic and metal, the metal being selected fromthe group consisting of at least one of iron, steel, copper, silver,gold, any alloys thereof, and any combinations thereof.
 3. The two-wireirrigation controlling and monitoring system according to claims 1 or 2,wherein said first plurality of controllable irrigation valves areoperated by a mechanism that is selected from the group consisting of amagnetic mechanism, an electrical mechanism, a hydraulic mechanism, apneumatic mechanism, and any combination of the aforesaid mechanisms,wherein said first plurality of controllable irrigation valves areopened by applying an inrush signal followed by a hold signal to saidpair of valve control inputs and closed by applying a zero signal tosaid pair of valve control inputs, and wherein said second plurality offield sensors comprises sensors selected from the group consisting oftemperature sensors, humidity sensors, pressure sensors, flow sensors,magnetic field sensors, mechanical movement sensors, mechanical strainsensors, fertilizer sensors and any combination of the aforesaidsensors.
 4. The two-wire irrigation controlling and monitoring systemaccording to either of claims 1 or 2, wherein said first alternating DCvoltage signal and said second alternating DC voltage signal alternatewith a frequency less than about 50 Hz.
 5. The two-wire irrigationcontrolling and monitoring system according to either of claims 1 or 2,wherein at least one of said first and second pulse widths of said firstalternating DC voltage signal and said second alternating DC voltagesignal is in the range 100 ms to 10 s.
 6. The two-wire irrigationcontrolling and monitoring system according to either of claims 1 or 2,wherein said voltage maximum is in a range from +10V to +20V, andwherein said voltage minimum is in a range from −15V to −25V.
 7. Thetwo-wire irrigation controlling and monitoring system according toclaims 1 or 2, wherein said first alternating DC voltage signal and saidsecond alternating DC voltage signal during said first pulse width andsaid second pulse width have an average voltage in the range −5V to−0.5V.
 8. The two-wire irrigation controlling and monitoring systemaccording to claims 1 or 2, wherein said current maximum is in the rangeof 0.5 A to 2 A, and wherein said current minimum is in the range 20 Mato 150 Ma.
 9. The two-wire irrigation controlling and monitoring systemaccording to claims 1 or 2, wherein said third pulse width is greaterthan said fourth pulse width, and wherein said fourth pulse width is inthe range 0.1 ms to 10 ms.
 10. The two-wire irrigation controlling andmonitoring system according to claim 3, wherein said line decoderprovides said inrush signal, said hold signal and said zero signal tosaid first plurality of controllable irrigation valves by supplying fromsaid pair of valve control outputs a pulsed alternating DC controlsignal to said pair of valve control inputs in accordance with saidtransmitted schedules of instruction, and wherein said pulsedalternating DC control signal defining a maximum voltage in the range of25V to 45V and a minimum voltage in the range of 0V to 5V, said linedecoder output pulse width defining a first part having said maximumvoltage and a second part having said minimum voltage, and wherein saidpulsed alternating DC control signal constitutes said inrush signal, byhaving said first part longer than or equal to said second part during aperiod in the range 10 ms to 1 s, and constitutes said hold signal andby having said first part shorter than said second part during a perioddetermined in accordance with said schedule of instructions transmittedto said line decoders by said controller and power supply unit.
 11. Thetwo-wire irrigation controlling and monitoring system according toclaims 1 or 2, wherein said schedules of instructions are transmittedonto said two-wire cable by re-scaling one of said first pulse width andsaid second pulse width to one of a first re-scaled pulse width in therange 10 ms to 49 ms indicating a binary “1” and a second re-scaledpulse width in the range 0.1 ms to 9 ms indicating a binary “0”, andwherein said schedules of instructions comprise a type of declarationdetermining additional content of a transmission from said controllerand power supply unit to said third plurality of localized irrigationcontrol units, said additional content being selected from the groupconsisting of an address of a specific designated localized irrigationcontrol unit of said third plurality of localized irrigation controlunits, data disclosing information regarding actions to be taken by saidspecific designated localized irrigation control unit of said thirdplurality of localized irrigation control units, and a first check and asecond check ensuring a safe reception of said transmission, whereinsaid transmission is terminated by a stop signal having a stop signalpulse width in the range of 50 ms to 70 ms.
 12. The two-wire irrigationcontrolling and monitoring system according to claim 11, wherein saidtype of declaration comprises 4 bits and provides 16 optional operationsselected from the group consisting of Arbitration, Data, Control(On/Off), Broadcast, Test, and Pole; wherein said address of saidspecific designated localized irrigation control unit of said thirdplurality of localized irrigation control units comprises an addresstransmission size in the range 0 to 128 bits; wherein said datadisclosing information regarding actions to be taken by said specificdesignated localized irrigation control unit of said third plurality oflocalized irrigation control units comprises a data transmission size inthe range of 0 to 64 KBYTE; and wherein said first check and said secondcheck ensuring a safe reception of said transmission comprise a checktransmission size in the range of 0 to 128 bits.
 13. The two-wireirrigation controlling and monitoring system according to claims 1 or 2,wherein a differential voltage is created in said two-wire cable, andwherein said controller and power supply unit comprises: amicroprocessor; a storage unit for storing said schedules ofinstructions; an output section for providing power to said two-wirecable and transmitting said schedules of instructions on said two-wirecable; and an input section for monitoring the voltage of said two-wirecable; wherein said microprocessor controls said output section to applysaid current minimum to said two-wire cable during an interrupt window;wherein each of said sensor decoders and line decoders comprises a shortcircuiting circuit providing (1) an interrupt signal during saidinterrupt window to said controller and power supply unit byunidirectionally short circuiting said pair of control and power supplyinputs, thereby reducing the differential voltage of said two-wirecable, and (2) a no interrupt signal by open circuiting said pair ofcontrol and power supply inputs, wherein said interrupt signal isconstituted by a voltage drop of said differential voltage of saidtwo-wire cable in the range of 5V to 35V; and wherein said interruptwindow is initiated following a DC alternation of said first alternatingDC voltage signal and said second alternating DC voltage signal and apower supply period in the range of 250 ms to 550 ms, wherein saidinterrupt window is in the range of 0 to 20 ms.
 14. The two-wireirrigation controlling and monitoring system according to claim 13,wherein said microprocessor records said interrupt signal from at leastone of said sensor decoders and line decoders of said third plurality ofsaid localized irrigation control units through said input sectionmonitoring voltage of said two-wire cable, and subsequently operatessaid ouput section to perform a DC alternation of said first alternatingDC voltage signal and said second alternating DC voltage signal, andoperates said ouput section to terminate said interrupt window and toapply said current maximum to said two-wire cable; and wherein saidmicroprocessor, following a recording of said interrupt signal from atleast one interrupting decoder selected from the sensor decoders and theline decoders of said third plurality of localized irrigation controlunits, performs a DC alternation of said first alternating DC voltagesignal and said second alternating DC voltage signal, and transmits atype declaration providing an Arbitration operation followed by a seriesof binary “1”s, including an answer window for said at least oneinterrupting decoder to answer to said binary “1”s; and wherein saidanswer window is initiated following a DC alternation of said firstalternating DC voltage signal, said second alternating DC voltagesignal, and a pause period in the range of 2 ms to 10 ms, whereby saidanswer window is in the range of 0 to 20 ms.
 15. The two-wire irrigationcontrolling and monitoring system according to claim 14, wherein saidshort circuiting circuit provides (1) an answer signal during saidanswer window to said controller and power supply unit byunidirectionally short circuiting said pair of control and power supplyinputs, thereby reducing the differential voltage of said two-wirecable, and (2) a no answer signal by open circuiting said pair ofcontrol and power supply inputs; and wherein said answer signal isconstituted by a voltage drop in said differential voltage of saidtwo-wire cable in the range of 5V to 35V; and wherein saidmicroprocessor controls said output section to supply said currentminimum to said two-wire cable during said answer window.
 16. Thetwo-wire irrigation controlling and monitoring system according to claim15, wherein said controller and power supply unit, during a declaredtype of transmission of schedules of instructions, requests saidspecific irrigation parameters from an addressed sensor decoder of saidthird plurality of localized irrigation control units, and subsequentlysaid controller and power supply unit transmits a series of binary “1”s,including said answer window, for said addressed sensor decoder toanswer said binary “1”s; and wherein said microprocessor (1) recordssaid answer signal from at least one sensor decoder of said thirdplurality of localized irrigation control units by using said inputsection to monitor said differential voltage of said two-wire cable, and(2) operates said output section to perform a DC alternation of firstalternating DC voltage signal and said second alternating DC voltagesignal, and (3) subsequently operates said output section to terminatesaid answer window and to apply said current maximum to said two-wirecable; and wherein said microprocessor interprets said answer signal asa binary “0” and a no answer signal as a binary “1”.
 17. A method forcontrolling and monitoring irrigation of localized areas of soil,comprising the steps of: providing water to said localized areas of soilthrough a water pipeline; controlling the discharge or supply of waterfrom said water pipeline; providing watering or non-watering of specificareas of said localized areas of soil through a first plurality ofcontrollable irrigation valves, positioned at said specific areas ofsaid localized areas of soil, said first plurality of controllableirrigation valves having a pair of valve control inputs; measuringspecific irrigation parameters through a second plurality of fieldsensors positioned at said specific areas of said localized areas ofsoil and said second plurality of field sensors having a pair of sensoroutputs; transmitting control signals to said first plurality ofcontrollable irrigation valves and said second plurality of fieldsensors though a third plurality of localized irrigation control unitscomprising a sensor decoder and a line decoder, providing valve controlsignals to said first plurality of controllable irrigation valves and/orrecording said specific irrigation parameters from said second pluralityof field sensors, each of said third plurality of localized irrigationcontrol units having a pair of valve control outputs connected to saidpair of valve control inputs of a specific controllable irrigation valveof said first plurality of controllable irrigation valves and/or a pairof sensor inputs connected to said pair of sensor outputs of a specificfield sensor of said second plurality of field sensors and having a pairof control and power supply inputs; providing a set of schedules ofinstructions by means of a controller and power supply unit having apair of control and power outputs supplying power by applying a firstalternating DC voltage signal defining a voltage maximum having a firstpulse width and defining a voltage minimum having a second pulse widthto one of said pair of control and power outputs, simultaneouslyapplying a second alternating DC voltage signal similarly shaped but ofinverted polarity as compared to said first alternating DC voltagesignal to another of said pair of control and power outputs and applyingan alternating DC current defining a current maximum having a thirdpulse width and defining a current minimum having a fourth pulse widthto said pair of control and power outputs; providing a two-wire cable,interconnecting said controller and power supply unit and said thirdplurality of localized irrigation control units through a two-wire cableconnecting said pair of control and power outputs of said controller andpower supply unit to said control and power inputs of said thirdplurality of localized irrigation control units and providing said powerfrom said control and power unit to each of said third plurality oflocalized irrigation control units; and transmitting said schedules ofinstructions from said controller and power supply unit to said thirdplurality of localized irrigation control units through said two-wirecable and receiving said specific irrigation parameters from said thirdplurality of localized irrigation control units through said two-wirecable.